I think Chen, Cheng, Chang, Zhang, Chan are all the same last name. Many Chinese people when they move to Vietnam changed their name to Tran which sounds similar also.
Rockbox: you're pretty close chen and chan are the same chang, tseng, zhang, cheng are the same (phonetically, it's pronounced "tzsang," if you can transition from the "tz" sound to "sang" quickly.) wang (Zhi Zhi), wong, hwang, huang are the same. (At least we aren't drafting someone from Thailand. There were 2 Thai kids in my grade school with names of Teppornabornasuthy and Kulapaditherom.)
Often, Chinese surnames that are phonetically the same have completely different characters (and are thus completely different names)... For example, the most common surname of Zhang (also pronounced as Chang) looks like the 2nd character from the right in this line: It sounds exactly the same (even has the same higher pitched 1st tone as this less common surname Zhang shown as the middle character in this line:
Chinese actress Ziyi Zhang's last name is the middle character in the second line. She played in "Crouching Tiger, hidden Draggon". For people from mainland China, Chang, Zhang, Cheng are three different last names. Wang and Huang are two different last names. People from mainland China are using the same rules to translate their names into English. As a result, one Chinese last name will have only one English translation. However, different Chinese last names may have the same English translation because their pronouciations are the same even though they are different characters. So, it is a multiple to one relationship when translating Chinese names into English names. Is this technical enough Since the Chinese in US are from all over the world. They use different rules or no rules at all to translate their names into English. So, the above prinple does not hold for people not from mainland China in recent years. Therefore, Chang, Zhang, Cheng represent the same Chinese last name in many cases.